The present invention relates to an encapsulated structure for plant initiate material, and particularly to delivery and germination of plant initiate material.
There are numerous techniques or methods for plant initiate material encapsulation. One of the most popular types is to use alginate as encapsulation material (see U.S. Pat. No. 4,562,663). A disadvanage of this type is that the concentration of alginate has significant impact over the germination of encapsulated plant initiate material. For example, the pressure resistance of capsule made of 3% alginate is approximately 1.2 Kg, a pressure sufficient to inhibit the germination of encapsulated plant initiate material. Although when alginate concentration is decreased to 2%, germination of encapsulated plant initiate material would not be affected, the pressure resistance becomes only 0.8 Kg, thus the artificial seed is too soft for rough handling. Another disadvantage of using alginate as encapsulation material is that alginate capsule is very sticky and dries out rapidly when exposed in the air (Redenbaugh et al., 1987 HortSci. 22:803).
To prevent water loss of the capsule, a new technique was developed whereby a membrane was coated on the alginate capsule. The number of the membrane coating depends on the requirements of the encapsulation (see U.S. Pat. No. 4,715,143). Unfortunately, once the membrane coating(s) prevents the capsule from drying out quickly, germination of the encapsulated plant initiate material is also restricted (Redenbaugh et al., U.S. Pat. No. 4,175,143; Redenbaugh et al., 1987. HortSci. 22:803).
U.S. Pat. No. 4,769,945 discloses a delivery unit for plant tissue whereby the capsule is made of water soluble material but its interior is covered with water insoluble material. During imbibition, the capsule can be dissolved upon contacting with water, thus, whether the waterproof layer can be broken through depends totally on the force generated by the germinating plant initiate material. Consequently, the germination of the encapsulated plant initiate material depends entirely on the rigidity and thickness of the waterproof layer. The major disadvantage of these methods is that small embryos, such as those from seeds of Cruciserae, may have difficulty penetrating through the waterproof layer.